1. Field of the Invention
The present invention relates to an image encoding method and an image encoding device using the image encoding method, and more particularly, to an image encoding method and an image encoding device for compressing an image using an imaging sensor of a video camera, a digital still camera, or the like.
2. Description of the Related Art
In recent years, in camera devices that include an imaging sensor, such as a digital still camera, a mobile phone with a camera, and a movie camera, an increase in the number of pixels has been advanced. On the other hand, a reduction in the amount of memory buffer and a reduction in power consumption are desired. In view of this, a method for reducing raw data (pixel data from an imaging sensor itself) from a sensor which consumes a memory buffer is considered. In this case, when performing irreversible compression, handling of defective pixel information of a sensor is a problem.
When image data including information indicative of a defective pixel is irreversibly compressed, there is a possibility that the information indicative of a defective pixel may be lost. Therefore, it is desirable to correct a defective pixel before compression but in view of memory and circuit costs incurred for a correction process, there is a desire to make good use in a sharing manner of external memory and circuit present in a subsequent-stage circuit for signal processing. This, in turn, results in that compression cannot be performed at a preceding stage for signal processing, causing a problem that it is difficult to reduce the amount of memory buffer and power consumption.
Also, there is a technique for referring to a code value obtained from a difference in pixel value between adjacent pixels, by a table value, as shown in Japanese Patent Laid-Open Publication No. 11-341288. Furthermore, there is a technique for encoding pixel information of the same color in DPCM encoding compression, as shown in Japanese Patent Laid-Open Publication No. 2000-244935.